Continuity mistake: In the final shoot-out scene where Clint Eastwood kills 5 men in rapid succession, Clint crouches and exchanges gunfire with two deputies who are standing side-by-side. A blood stain suddenly appears on the abdomen of the younger deputy on the left, but there is no bullet hole, it does not coincide with any gunshot sound effect, and the deputy does not react to the wound. A moment later, as Clint continues firing, both deputies topple over backwards.
Continuity mistake: In the bar scene where Gene Hackman confronts Clint Eastwood there is a whiskey bottle and a glass on the table in front of Eastwood. He shoves the glass forward and you definitely hear it chink against the bottle. In the next second there are several inches of space between the bottle and the glass.
Continuity mistake: When "The Schofield Kid" kills "Quick Mike" in the outhouse, all of the shots are to the chest. In the cutaway shot of the dead Quick Mike, he has a bullet hole in his forehead.